Re: Questions re subqueries

From: Luke Davies <luke.davies@xxxxxxxxxxx>

To: wjwagman@xxxxxxxxxxx

Date: Wed, 20 Jun 2007 09:07:32 +0100

A NULL will not equate to anything not even NULL, and also a NULL will
not NOT equate to anything either. So ...

select count(*) from dual
where NULL = NULL
Will get zero rows
select count(*) from dual
where NULL != NULL
Will get zero rows

Basically you will get a false result using NULLs unless you use the
special syntax IS NULL or IS NOT NULL. Also DECODE will allow you to
equate NULL.

HTH
Luke
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